Combine finely diced fresh strawberries and granulated sugar in a medium saucepan over medium heat. Cook for about 45 minutes, mashing the strawberries halfway through. Stir occasionally until the jam thickens, then set aside to cool.

Blend softened cream cheese, granulated sugar, and vanilla extract until smooth. Divide into 18 equal portions, flatten each into a disc, and freeze for at least 30 minutes.

Beat softened unsalted butter and granulated sugar until light and fluffy. Add the egg and a splash of vanilla extract, mixing until fully incorporated.

Whisk together all-purpose flour, baking powder, and salt in a separate bowl. Gradually add to the butter mixture, stirring gently until just combined.

Divide cookie dough into four equal parts, spoon a layer of thick homemade strawberry jam onto each layer, then fold corners to encapsulate jam. Scoop 18 portions ensuring a cheesecake disc is at the center.

Preheat oven to 350°F (175°C). Arrange cookie discs on a parchment-lined baking sheet, bake for 11-12 minutes until edges are golden and centers are soft. Cool on tray for 10 minutes before transferring to a wire rack.